In the past few decades, telephone systems have evolved continuously at an accelerated rate. A long term evolution (LTE) system, initiated by the third generation partnership project (3GPP), is now being regarded as a new radio access technology (RAT) and core radio network architecture that provides a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, an evolved universal terrestrial radio access network (EUTRAN) includes a plurality of evolved Node-Bs (eNBs) and communicates with a plurality of mobile stations, also referred to as user equipments (UEs).
Another evolution in telecommunications is the introduction of femtocells. A femtocell is a small cellular base station, typically designed for use in a home or small business. Femtocells generally connect to the service provider's network via broadband (such as DSL or cable); current designs typically support 2 to 4 active UEs in a residential setting and 8 to 16 active mobile phones in enterprise settings. A femtocell allows service providers to extend service coverage indoors, especially where access would otherwise be limited or unavailable. In LTE terms, femtocells are called Home eNode Bs (HeNBs) and are one type of RAT object. A RAT object, or measurement object, generally is an object on which the UE shall measure measurement quantities and corresponding object information. The RAT object may include a single cell, or a list of cells to be considered as well as associated parameters, e.g. frequency-specific offsets or cell-specific offsets. HeNBs are typically associated with uncoordinated large-scale deployments of several HeNBs in one or more closed subscriber groups (CSGs) and, therefore, the connection to the operator's core network needs to be realized efficiently. A CSG is a specific group of UEs permitted access to a femtocell. A CSG-ID is broadcast from the femtocell in a system information block (SIB) message and only those UEs who are members of this group, as defined by a CSG white list of CSG IDs (generally stored on the UE), will attempt to select the cell.
Before deciding to hand over a UE to a CSG, the eNB (or Macro eNB) generally needs to acquire UE measurement information related to the target CSG cell. In order to allow the UE to make those measurements efficiently, a newly defined proximity report can be configured within the UE via a radio resource control (RRC) connection reconfiguration message. This proximity report will allow the UE to send a so-called “proximity indication” to the source eNB whenever it is entering or leaving the proximity of one or more cells with CSG IDs in the UE's CSG whitelist. A UE that is able to determine that it is near its CSG cell can thus tell the network to take the necessary actions for measurement or handover preparation.
An RRC connection reconfiguration procedure is used by the RRC layer of the EUTRAN to modify a UE's RRC connection, e.g., to establish/modify/release radio bearers, to perform handover, or to set up/modify/release measurements. When the UE receives an RRC connection reconfiguration message, the UE performs an RRC connection reconfiguration procedure based on information within the message. For example, the EUTRAN can configure the UE to report measurement information to support the control of UE mobility to a CSG. Additionally, the EUTRAN can configure, via an RRC connection reconfiguration message, the UE for an inter-RAT handover from a legacy wireless network (GPRS, UTRA, CDMA2000) to the EUTRAN. However, receiving and processing the RRC connection reconfiguration message is costly in terms of delays and the amount of battery power required by the UE to comply with RRC messages.